I beleive they are talking about 8th amendment, I don’t know if 18th amendment even exists.
We are not living in old times when a new king orders to re-write history from his own perspective, I agree thread title is however misleading towards that. They want to remove 8th amendment from constitution which specifically granted title to Ziaul Haq. So by removing that provision the constitution will no longer carry the name of Ziaul Haq in its entirety (apparently).